Denture



I Patented Aug. 10, 1931 UNITED. STATES A PATENT OFFICE DENTURE EnriqueG. Touceda, Albany, N. Y., assignor to Consolidated Car-Heating Company,Inc., Albany, N. Y., a corporation of New York My invention relates toprosthetic articles and particularly to dentures and the like formedfrom metal, and preferably but not necessarily, by the process ofcasting.

In the making of dentures by casting, it is usual to take an impressionin plastic material of the interior mouth and jaw structure. Thisreproduces exactly, in the, plastic, all of the small irregularities ofthe mouth and jaw structure and is used in making a pattern from whichthe denture is cast from a suitable metal or alloy.

In order exactly to reproduce in the cast article all the minutestructural irregularities in the pattern, the metal used must have manypeculiar characteristics among which the following are of paramountimportance: It must be highly fluent at casting temperatures because ifit is viscous or sluggish when molten it will not run freely into thefiner details of the mold.

This is particularly true where a skeleton bridge, plate or otherstructurehaving finely attenuated portions is being cast, but it is alsotrue in the casting of full or partial plates of paper thickness whereit is necessary to produce an article conforming exactly to all of thefiner rugae of the patients mouth.

The metal, in the as cast condition, must have a clean surface so thatgrinding and polishing is substantially unnecessary or at least is re..

39 duced to an absolute minimum. Since the exterior surface of thedenture, as cast, conforms to the irregularities of the pattern andsince many of these are of an extremely delicate nature, the removal ofany substantial portion of the 1 surface of the casting destroys the fitthereof.

The metal used must be such that the shrinkage of the casting on coolingis extremely small otherwise it is impossible to obtain a cast den- 4ture which fits properly due to the impossibility,

arising from the particular nature of the patacid which is invariablypresent in the mouth.

The metal must be strong, hard and highly resistant to deformation evenin attenuated sections. Yet, on the other hand, it must be capable ofbeing bent to a considerable degree without fracture in order thatbridges, clasps and the like may be properly fitted. The yield denturesmade therefrom may be subjected to the distortion necessary in close andproper fitting without producing permanent deformation.

The melting point should be as low as possible not only to minimize the.cost and the natural diificulties encountered in casting metals oralloys having extremely high melting points, but also to minimizeshrinkage on cooling; and the specific gravity of the composition shouldalso be as low as possible in order that the dentures may be light inweight.

An alloy comprising principally nickel and chromium and containing byweight from to of nickel and from 5% to 30% of chromi.. um affordsexcellent possibilities for use in making dentures because of its costas compared with the precious metals and also because of its highresistance to the corrosive agents ordinarily encountered by dentures.However, such a composition is quite soft, the melting point isextremely high, and the alloy when molten is so viscous that it isimpossible to cast thin sections therefrom. Moreover, the surface of thealloy in the as cast condition is not suitable for dentures because ofthe dirt and scale which must be removed therefrom by grinding andpolishing.

I find, however, that these undesirable characteristics of, achromium-nickel alloy of the above type may be eliminated or modified toa suflicient degree to make possible its use in dentures byincorporating therein small proportions of beryllium, say from 0.1% to5% by weight. While such additions do not affect the highly desirablecorrosion resisting characteristics inherent in the chromium-nickel basealloy, they do appreciably lower its melting point, increase itsfluidity at casting temperatures to such an extent that extremelyattenuated sections may be readily cast, and improve the surface of thecasting to such a degree that a very light polishing is all that isrequired to complete the article. Moreover, the hardness of the alloyand the yield point thereof are substantially increased. In other words,by the addition of beryllium it is possible to make an otherwise totallyunsuited alloy extremely well adapted for dentures.

In making my alloy the nickel and chromium are first melted together,and the beryllium, which has a very low specific gravity and isreadilyoxidizable, is thereafter added. Due to the lightness of theberyllium, it should be prealloyed with a suitable heavier metal, suchas nickel or copper, and the addition made by tying the nickel-berylliumor copper-beryllium to a rod and plunging it into the molten mass. Oncethe nickel-beryllium or copper-beryllium is wet ,it alloys readily. Justbefore the molten mass is poured I prefer to add a small amount ofcalcium, say 0.05% as a deoxidizer.

My preferred composition contains nickel around 80%, and chromium around20% with suflicient beryllium to obtain the desired results. This willgenerally be well under 5%, and since beryllium at the present time isquite expensive the quantity employed will naturally be as small aspossible. However, the presence of an extremely small quantity ofberyllium is readily noticeable in its eflect on the characteristicsabove mentioned of the alloy; as little as 1%,

for example,- lowering the melting point as much as 120. The efl'ects ofthe beryllium, however, are more'especially marked when the quantity isin excess of 2%.

In addition to eflecting the essential changes in the base compositionabove noted, the beryllium, because of its extreme lightness, effects avery substantial reduction in the specific gravity of the compositionwhich is another extremely desirable feature of the alloy when used fordeutures.

The term denture as used herein and in the appended claims is to beunderstood as including inlays, crowns, plates, clasps and otherstructures intended for use in the mouth, and also prosthetic articlesin general.

What I claim is: v

1. A denture formed from an alloy having nickel and chromium as itsprincipal alloying ingredients and containing nickel from 65% to 90%,chromium from 5% to and beryllium from 0.1% to 5%.

2. A cast denture formed from an alloy having nickel and chromium as itsprincipal alloying ingredients and containing nickel from to 90%.chromium from 5% to 30% and beryllium from 0.1% to 5%..

3. A denture formed from an alloy having nickel and chromium as itsprincipal alloying ingredients and containing nickel from to chromiumfrom 15% to 25% and beryllium

